1. Field of the Invention
This invention relates generally to apparatus and methods for cooling electronic heat generating components within a cabinet and more particularly to a method and apparatus for cooling electronic components wherein predetermined heat generating electronic components are isolated from other electronic components in the cabinet and the isolated components are cooled by a secondary air flow isolated from the primary air flow through the cabinet such that the non-isolated components and the isolated components are independently cooled by the primary air flow and secondary air flow, respectively, and the heat generated by the isolated components and non-isolated components is not mixed within the cabinet to maximize cooling of all components within the cabinet.
2. Brief Description of the Prior Art
A common problem in electronic packaging is that the heat generated by the electronic components in the cabinet is detrimental to the components themselves, particularly integrated circuits and microprocessor chips in computer cabinets. Heat is normally removed by circulating air across the components by one or more low powered exhaust fans mounted in or on the computer cabinet.
The microprocessor chip in a computer generates a relatively large amount of heat and is susceptible to error or damage caused by overheating. For example, the Intel 80486 microprocessor chip generates 4.5 watts in normal operation and must be maintained below 85.degree. C. or it can introduce error as well as reduce its operating life. Even newer chips will generate 15-30 watts. To assist heat removal from an integrated circuit chip, a heat sink is often mounted on the top surface of the chip. Heat sinks are metal devices that have a plurality of fins or pins extending from a base which is mounted on the chip surface to radiate or transmit heat from the chip to the circulating air. The fins are usually aligned longitudinally with the prevalent direction of air flow and when the air flow direction is uncertain, pin-type heat sinks may be used.
The exhaust fan in a computer cabinet usually develops a single air flow path wherein air from the cabinet exterior is drawn in through inlet slots in the cabinet wall flows across the components including the heat sink and is exhausted through exhaust slots in the fan motor housing in another wall of the cabinet. Although the heat sink is useful in cooling the microprocessor chip, the heat generated by the heat sink is mixed with the heat generated by the other components in the cabinet such that the effective cooling of all the components including the ones having heat sinks is diminished.
Others have attemted to solve the heating problem by mounting a small supplementary fan on the heat sink, and mounting liquid cooling devices (water jackets) or devices utilizing the Peltier effect on the chip to be cooled.
The present invention overcomes the heating problem by isolating predetermined heat generating electronic components which may include those with heat sinks from other electronic components in the cabinet and providing a secondary air flow pathway from the air inlets across the isolated electronic components to the air outlets and exhaust fan. The secondary air flow is isolated from the primary air flow. The exhaust fan in or on the cabinet creates a primary air flow across the non-isolated components between the air inlets and air outlets in the cabinet and exhausts the air to the cabinet exterior, and simultaneously creates a separate secondary air flow through the secondary air flow pathway across the isolated heat generating components between the air inlets and air outlets in the cabinet and exhausts the secondary air flow to the cabinet exterior. Thus, the non-isolated components and the isolated components are independently cooled by the primary air flow and secondary air flow, respectively, and the heat generated by the isolated components and non-isolated components is not mixed within the cabinet to maximize cooling of all components within the cabinet.